This invention relates to machines for making plastic bags, and more particularly to an improved bag punching and slitting device for such machines. Even more particularly, this invention relates to improved means for releasably mounting bag punching and slitting devices on such machines.
There are presently available a number of machines which are employed for manufacturing plastic bags out of thermoplastic materials. One such machine is disclosed in the U.S. Pat. No. 3,802,308, which was granted Apr. 9, 1974. In a machine of this type, overlapping webs of a thermoplastic material are passed beneath a so-called punching and slitting device, which reciprocates toward and away from the overlapping plastic webs in order simultaneously to form adjacent slits and perforations in what is to be the open end of a respective bag. Typically each such punching and slitting device comprises a punching element having a circular, generally serrated edge, and a cutting blade which is mounted in the device in spaced, adjacent relation to the punch.
In the above-noted U.S. Pat. No. 3,802,308, for example, a pair of such punches and their associated cutting blades are secured in a conventional manner by screws or bolts to a plate 92. Plate 92 is fastened, also in a conventional manner, to the piston of an air cylinder, so that the plate and the attached punches and cutter blades can be reciprocated toward and away from the plastic bags. Similarly, U.S. Pat. No. 3,196,728 discloses a cutting blade and punch that are mounted side by side on a plate which is attached to the lower end of a piston, that is operable to reciprocate the plate, and hence the attached punch and slitter blade, toward and away from a bag of transparent plastic material, thereby simultaneously to punch and slit the bag. Again, however, the punch and blade are mounted on the reciprocable support plate in a very conventional manner, and the support plate in turn is fastened to the piston shaft by conventional threaded fittings.
A major problem with existing mounting devices for punches and slitter blades of the type described is that, whenever it is necessary to change a punch and/or slitter blade, or to change or remove the punch and blade holder device, it is necessary to shut down the associated bag making machine. These changes therefore can be very time consuming and expensive to effect, and often require the use of skilled labor.
It is an object of this invention, therefore, to provide improved means for mounting bag punching and slitting devices in bag making machines of the type described.
Another object of this invention is to provide improved mounting means of the type described which enables a bag punching and slitting device to be installed in or removed from a bag making machine of the type described extremely rapidly and by use of a simple tool.
More particularly, it is an object of this invention to provide a novel quick slip holder, which can be quickly and easily operated by an unskilled operator to effect a rapid change and/or adjustment of punches and slitting blades of the type described.
Other objects of the invention will be apparent hereinafter from the specification, and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.